Surface-confined monomers on electrode surfaces. 6. Adsorption and polymerization of 1,6-diisocyanohexane on Au and Pt

Thin films of 1,6-diisocyanohexane (DICH) can be formed on Au and Pt surfac es by immersion of clean substrates in 0.001-1.0 M solutions of DICH. Infra red transitions for both Au-bound and free isocyanide functionalities are o bserved after Au surfaces have been placed in methanolic solutions with DIC H concentrations >0.001 M, indicating that some portion of the DICH layer i s composed of molecules with only one of the isocyanide moieties bound to t he Au surface. In addition, poly(DICH) layers are formed on Au as noted by the presence of imine bands in the reflection-absorption infrared (RAIR) sp ectra of such surfaces and the time-dependent nature of the band intensitie s of the imine and methylene modes. The resulting DICH-coated Pt and Au sur faces are effective transport barriers-substantially diminished redox respo nses of various solution probes are observed at such modified electrodes. I n particular, the DICH films on Pt prevent 95% oxidation of the underlying metal surface. It is found that the remaining free isocyanide groups on the DICH-coated surfaces can be further polymerized (cross-linked) to various extents by exposure to oxygenated aqueous Ni2+ solutions, allowing for cont rol of film permeability. These results point to the possible application o f poly(DICH) films in the fields of chemical sensing and corrosion protecti on.